ForumSpringerAstron. Astrophys.
ForumWhats NewSearchOrders

Astron. Astrophys. 325, 915-922

Table of Contents
Available formats: HTML | PDF | (gzipped) PostScript

Surface photometry of the edge-on spiral NGC 4565*

I. V-band data and the extended optical warp

Magnus Näslund and Steven Jörsäter

Stockholm Observatory, S-133 36 Saltsjöbaden, Sweden (magnus@astro.su.se, steven@astro.su.se)

Received 5 July 1996 / Accepted 13 January 1997


We have studied the faint luminous parts of the disk of NGC 4565 in the radial and z-directions. The semi-major axis profiles follow exponentials until a break in the luminosity profiles occurs. Beyond the breaks the luminosity distributions are well fitted by steeper exponentials and continue with a constant slope to the limit of the data around .

A recent discovery of a faint luminous halo in NGC 5907 has raised the question whether there is a luminous population tracing the dark mass in spiral galaxies. The vertical profiles of NGC 4565 fall off less steeply than those of NGC 5907 which to a large extent is explained by the combination of a thin disk and a photometric thick disk. The outer profiles are more shallow, in agreement with previous studies, giving a hint of a third component or of the response of the inner parts to the dark-halo mass. The constancy of scaleheight with radius in the outer parts is confirmed.

The marginal NW stellar warp is also confirmed, but more interestingly there is a faint extension of this optical warp, which coincides with the H I warp, and therefore most likely is physically connected to the galaxy. This finding indicates that star formation may occur outside the disk cutoff in spiral galaxies.

Key words: galaxies: halos - galaxies: NGC 4565 - galaxies: photometry - galaxies: spiral - galaxies: structure - dark matter

*Based on observations collected at the Nordic Optical Telescope, La Palma, Spain

Send offprint requests to: M. Näslund

© European Southern Observatory (ESO) 1997

Online publication: September 9, 1997
Last change: April 28, 1998